Seasonal and successional patterns of phytoplankton in Epe Lagoon, Lagos, Nigeria
Variations in phytoplankton species abundance and composition are regulated by changes in physico-chemical factors. A study of biodiversity and successional sequences was carried out monthly from November 2012 to April 2014 to determine the environmental factors controlling phytoplankton assemblages in Epe Lagoon, Lagos, Nigeria. Surface water and phytoplankton samples were collected from 12 stations within the lagoon. Physico-chemical analyses and phytoplankton biodiversity were carried out using American Public Health Association (APHA) protocols and light microscopy, respectively. A canonical correspondence analysis and the Pearson correlation coefficient (r) were used to determine the relationship between physico-chemical parameters and different phytoplankton divisions identified within the lagoon. Five phytoplankton divisions (Bacillariophyta, Chlorophyta, Cyanobacteria, Euglenophyta and Pyrrophyta) were represented within the lagoon. Higher phytoplankton biomass was recorded in the dry season (November to April) than in the wet season (May to October). Centric diatoms (Aulacoseira granulata var. angustissima O. Mull and Melosira granulata (Ehr.) Ralfs) dominated the phytoplankton spectrum throughout the study period, except in June and July 2013, when Mougeotia sp. was dominant. Rainfall distribution patterns primarily determined the physico-chemical environment, whereas salinity, calcium ions, hydrocarbons (oil and grease), conductivity, total dissolved solids (TDS), turbidity and silicate were the major factors controlling phytoplankton dynamics during the study period.
Keywords: biodiversity, canonical correspondence analysis, centric diatoms, community structure, Pearson correlation coefficient, physicochemical parameters